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R Hübner

Publications and source records attributed to R Hübner.

At least 37 records · Page 2Linked to original sources
PubMed1996

Specific effects of spatial-frequency uncertainty and different cue types on contrast detection: data and models.

If the spatial-frequency of sinusoidal signals in a contrast-detection experiment varies randomly from trial to trial, then performance is decreased compared with that in a situation where it remains constant. This spatial-frequency uncertainty effect can more or less be compensated by presenting informative cues shortly before each trial. Single-band, as well as multiple-band models, have been proposed to explain the uncertainty and cuing effects. While the latter assume that under uncertainty multiple channels are monitored simultaneously, the former propose that in each trial a single, but sometimes inappropriate, channel is selected for monitoring. Until now it is open which of these models is valid. Therefore, psychometric functions were collected under different conditions of spatial-frequency uncertainty. It appears that the size of the uncertainty effect varies with spatial-frequency. This result can be explained by a multiple-band model, as computational analysis reveals.

Adult↗
PubMed1995

Cuing mechanisms in auditory signal detection.

Detection of auditory signals under frequency uncertainty can be improved by presenting cues to the listeners. Since various cues have been found to differ in effectiveness, three conceivable mechanisms were considered which might account for these differences. Cuing might reduce the number and/or width of the employed auditory filters or listening bands. Also, cues could modulate the precision of frequency tuning of the filters. Psychometric functions were collected in a detection experiment with frequency uncertainty employing three kinds of cues: pure tones whose frequency was identical to that of the signal (iconic cues), complex tones with a missing fundamental equal to the signal (complex cues), and pure tones with a certain frequency relation to the signal (relative cues). Compared with a no-cue condition, all cue types improved detection performance. Fitting models to the data suggests that in the no-cue condition as well as the complex-cue condition, multiple bands were utilized, and that the iconic and relative cues induced single-band listening. There is no indication that accuracy of frequency tuning was responsible for cue-efficiency differences.

Attention↗
PubMed1994

The HSR on chromosome 1 of the house mouse, Mus domesticus: distribution and frequency in Switzerland.

A total of 357 house mice (Mus domesticus) from 83 localities uniformly distributed throughout Switzerland were screened for the presence of a homogenously staining region (HSR) on chromosome 1. Altogether 47 mice from 11 localities were HSR/+ or HSR/HSR. One sample of 11 individuals all had an HSR/HSR karyotype. Almost all mice with the variant were collected from the Rhone valley (HSR frequency: 61%) and Val Bregaglia (HSR frequency: 81%). For samples from most of the area of Switzerland, the HSR was absent. There was no strong association between the geographic distribution of the HSR and the areas of occurrence of metacentrics. However, at Chiggiogna the HSR was found on Rb (1.3). Possible explanations for the HSR polymorphism are discussed.

Animals↗
PubMed1993

Additivity of loudness across critical bands: a critical test.

The use of magnitude estimation as well as axiomatic measurement theory has led to the suggestion that loudness adds across critical bands. In the present paper, we challenge this postulate by applying a more sensitive methodology, based on Falmagne's (1976) random conjoint measurement procedure. A necessary condition for additivity of loudness was investigated in tone complexes consisting of 2-kHz and 5-kHz (resp. 3-kHz) components; the results showed systematic deviations from additivity. We argue that these deviations are due to asymmetric masking of the higher component by the lower one, and we propose a tentative quantitative model to account for the data. Such a model is in line with results from tone-on-tone masking, which show masking to be effective over a range of several critical bands.

Auditory Threshold↗
PubMed1993

Different ways of modeling spatial-frequency uncertainty in visual signal detection.

Inferior human signal-detection behavior compared with that of ideal observers has been explained by intrinsic uncertainty of the human observer with respect to certain signal parameters. One way to model this uncertainty is to assume that the observer simultaneously monitors multiple channels, corresponding to possible parameters. However, it is also conceivable to assume that an observer, uncertain about which channel to monitor, chooses a suboptimally tuned single filter. Finally, uncertainty may also cause the filter underlying a single channel to broaden. In this paper these different models are investigated with respect to spatial-frequency uncertainty for matched filters detecting Gabor signals. All three mechanisms predict a decrease in detection performance. However, it is shown that the resulting psychometric functions are different. While the slopes increase with uncertainty for the multiple-channel models, they decrease for a randomly chosen single channel. Broadening a single filter leads to parallel psychometric functions.

Humans↗
PubMed1991

The karyotype of the middle-African hedgehog Atelerix albiventris Wagner, 1841 and its cytotaxonomical relationships to other Erinaceinae (Insectivora: Erinaceidae).

Like other hedgehog species investigated hitherto, also the Middle African species Atelerix albiventris has a diploid number of 48 chromosomes. However, Aethechinus and Atelerix display quite distinct cytogenetic characteristics compared to the hedgehog genera Erinaceus, Hemiechinus and Paraechinus. Individual chromosome structures and reactivities permit the recognition of similarities to the Algerian hedgehog Aethechinus algirus and indicate their close relationship. Nevertheless, the proposal by Corbet (1988) to merge the two taxa into one genus, which is contrary to Robbins and Setzer (1985) remains to be clarified by further investigations.

Animals↗
PubMed1990

[Therapy of perioperative myocardial damage in aortocoronary venous bypass surgery].

The perioperative lesion of the myocardium in heart-lung machine operation can on principle not be prevented despite complex measures of the protection of the myocardium and the individual monitoring of the patients, this particularly by including patients with high risk of ischaemia of the myocardium (instable angina pectoris, stenosis of the trunc and greatly restricted left-ventricular function, respectively) in former years. In a proved perioperative lesion of the myocardium the limitation of the myocardial lesion stands in the centre of intensive-medical measures with vasodilators and positive inotropic substances.

Cardiac Output, Low↗
PubMed1990

Cytogenetic studies on wild house mice from Belgium.

The present status of Robertsonian karyotype variation in populations of wild mice from Belgium is presented. Two fusions, Rb(4.12)1Nam and Rb(5.10)3Nam, were identified in the central plain of this flat country. Surrounding this region only mice with the usual 2n = 40 karyotype occurred. From the distribution pattern some possible relationships to other Rb populations from Europe are discussed.

Animals↗
PubMed1990

Is there an auditory analogue to Fechner's paradox in binaural loudness perception?

In binocular brightness perception a phenomenon called Fechner's paradox can be observed. This paradox implies non-monotonicities in the psychometric functions of binocular brightness. Lehky (1983) proposed a model that describes such non-monotonicities. He suggested that Fechner's paradox also exists in binaural loudness perception. However, until now no sufficient data have been collected to test this hypothesis. Therefore, an experiment was conducted in which 36 psychometric functions were obtained using binaural stimuli in the range of intensities in which Fechner's paradox supposedly occurs. As a result, no significant non-monotonicities were found. However, it is shown that jnds derived from the psychometric functions contradict predictions derived from the limited binaural additivity model of Gigerenzer and Strube (1983).

Adult↗
PubMed1990

[Experiences with gamma-2-free amalgam].

Within a clinical examination the Gamma-2-containing Amalgam "Dentargam", the Gamma-2-reduced "Germadent" and the Gamma-2-free alloy "Duragam" are tested by an intraoral comparison of tooth-paars. A superiority of the alloys with reduced Gamma-2-phases was found.

Dental Amalgam↗
PubMed1990

[10 years' comparison of inpatient treated affective diseases].

A comparison was carried out between 237 hospitalised patients with emotional disorders during the years 1972-1975, and 316 patients between 1982 and 1985. The number of admissions as a percentage of all psychiatric admissions rose from 18.21% to 26.49%. There was a significant rise in the number of readmissions, notably from the third admission upwards, but a considerable reduction in the length of stay in hospital. During the period the number of admissions to general hospitals within the catchment area was reduced by about one half, with the result that there was no appreciable overall increase in the number of admissions for in-patient treatment of emotional disorders in the ten-year period.

Bipolar Disorder↗
PubMed1989

[A dynamic model of loudness adaptation].

Previous research on loudness adaptation has provided heterogeneous and partly contradictory results. One major reason seems to be the inconsistent use of the term 'adaptation', which is due to differing operational definitions. Here, a measurement-theoretic definition of loudness adaptation is introduced, which also comprises a new method for the identification of certain linear dynamic systems. This is of particular interest, since there is a lack of dynamic models describing loudness adaptation. An experiment with sinusoidal sound stimuli (3000 Hz) was performed to test whether loudness adaptation can be modeled by such a linear system. The results of the system identification indicate that this is possible. Therefore, it can be concluded that the given definition of loudness adaptation might be appropriate and that the method of system identification is an applicable research tool.

Adult↗
PubMed1989

[Seasonally-related inpatient admission of affective patients].

Over a period of four years, 316 emotionally disordered patients were inspected for the frequency of seasonally conditioned hospitalisation, considering however solely the most recent prior hospitalisation within the four-year period. A cautious interpretation of the results would suggest significant differences in the seasonal frequency of emotional disorders that have resulted in hospitalisation. Manic depressive disorders, endogenous depression, and involutional depressions treated in hospital occur with the greatest frequency in autumn. These results suggest the possibility of employing thymoleptic treatment, notably to effect an influence on biorhythms, for instance, lithium, deprivation of sleep, and bright-light therapy.

Depressive Disorder↗
PubMed1986

Transmission of bovine leukemia virus (BLV) to immunocompromised monkeys: evidence for persistent infection.

Splenectomized or irradiated adult and untreated baby macacques were infected with bovine leukemia virus from continuously virus producing fetal lamb kidney cell cultures. Persisting high antibody titers were followed for 4 years in the adult and 16 months in the baby monkeys, using an ELISA technique. With the exception of a persistent leukocytosis in one adult monkey, the animals remained healthy throughout the observation period. Transfer of lymphocytes from this animal to a seronegative recipient led to anti-BLV seroconversion with a lag of 5 months. All other transfer experiments showed a negative result. Virus could be recovered from the newly infected baby macacques by means of lymphocyte/fetal lamb kidney cell cocultivation for up to 4 weeks after inoculation. All other attempts to recover virus from the infected animals at a later point were unsuccessful.

Animals↗